Servo action parking brake with rotary actuator

ABSTRACT

A sliding caliper disk brake assembly incorporating a hydraulic, service actuator and a mechanical, parking actuator. The mechanical actuator includes an annular cam that is disposed concentrically with the piston of the hydraulic actuator to provide a compact assembly. An arrangement is also incorporated for generating a self-energizing force when the brake is mechanically actuated.

United States Patent [191 Hendrickson July 3, 1973 [54] SERVO ACTIONPARKING BRAKE WITH 2.814.366 11/1957 Luliien Uzi/8136 P ARY 3.371.7503/1968 Sc utte et a 1.8 ROT ACTUATOR 3.532.196 10/1970 Winge 188/722[75] Inventor: Paul G. Hendricks-on, Ann Arbor.

Mich v FOREIGN PATENTS OR APPLlCATlONS 1.129.106 l0/1968 G t B ta'l88/72.7 [73] Assgnee Hayes 1.489.537 6/1967 Fr ::ce.: Isa/72.2

[22] Filed: Oct. 27, 1970 Primary Examiner-George E. A. Halvosa [211 AppNo: 86 n8 Attorney-Harness, Dickey & Pierce [52] U.S. Cl. 188/722,188/726, 188/106 F, [57] ABSTRACT 188/196 9 A slldmg caliper dlSk brakeassembly Incorporating a 511 1m. 0. Fl6d 55/46 hydraulic, Serviceactuator and a mechanical. Parking 5 Field f Search 183/713, 7 726actuator. The mechanical actuator includes an annular 1 /72 10 F, 19 Pcam that 15 disposed concentrically with the P151011 0f the hydraulicactuator to provide a compact assembly. [56] References Citd Anarrangement is also incorporated for generating 21 UNITED STATES PATENTSself-energizing force when the brake is mechanically t t d. 3,266,6028/1966 Belart et al. 188/726 X ac a 8 3,321,049 5/1967 Swift 188/722 X 6Claims, 6 Drawing Figures ,7/ f A 9 f? I/ /7 5:" 'j M 1 X4 p/ J )7; 5, Q4 J;

[2 1k if PATENTEDJULB ms I 3 743 050 fla /'24.

SERVO ACTION PARKING BRAKE WITH ROTARY ACTUATOR BACKGROUND OF THEINVENTION This invention relates to a disk brake assembly and moreparticularly to an improved disk brake assembly incorporating a servoaction parking brake with a rotary actuator.

The application of disk brakes to motor vehicles has been limited to useon the front wheels, except for certain high priced or special purposevehicles. One reason disk brakes have not been used with the rearvehicle wheels is the difficulty in providing a satisfactory mechanicalactuator for the parking brake function. In most instances, separateparking brakes are provided although it has been proposed tomechanically actuate the same brake pads that are actuated by thehydraulic, service actuator. Most of the arrangements provided for thecombined hydraulic and mechanical actuation of the disk brake pads areextensive and do not lend themselves to high volume production.

It is, therefore, a principal object of this invention to provide animproved hydraulic and mechanical actuator for a disk brake.

It is another object of this invention to provide a simplifled, combinedservice and parking brake of the disk type.

It is a further object of the invention to provide an improvedmechanical actuator for adisk brake.

Another reason why disk brakes have not been employed for parking brakesis that disk brakes do not normally provide any self-energization orservo action. Thus, in the absence of some form of power assistsufficient forces cannot be generated with conventional mechanicalactuated disk brakes.

It is, therefore, still another object of this invention to provide acombined service and parking brake that provides a servo action whenmechanically actuated.

SUMMARY OF THE INVENTION This invention is adapted to be embodied in acombined hydraulic and mechanicalactuator for a disk brake or the like.The actuator includes a housing that defines the cylinder bore of afluid motor. A piston is received in the cylinder bore, and the pistonand housing are relatively movable along the axis of the cylinder boreupon pressurization of the cylinder bore to actuate a brake pad or thelike. Annular cam means are juxtaposed to the cylinder bore. The annularcam means includes an element supported for pivotal movement and meansfor effecting a force substantially in the direction of the axis of thecylinder bore upon pivotal movement of the element for actuating thebrake pad.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross sectional view ofadisk brake assembly embodying this invention taken along the line 11 ofFIG. 2.

FIG. 2 is a cross sectional view of the brake taken along the line 22 ofFIG. 1.

FIG. 3 is an enlarged cross sectional view taken along the line 3-3 ofFIG. 2.

FIG. 4 is a cross sectional view taken generally along the line 4-4 ofFIG. 3.

FIG. 5 is an enlarged cross sectional view taken along the line 5-5 inFIG. 2.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An automotive diskbrake assembly embodying this invention is identified generally by thereferencenumeral 11. The disk brake assembly 11 is particularly adaptedfor use in braking the rear wheels (not shown) of a motor vehicle. Thewheel is adapted to be connected to the hub 12 of a rear axle 13. Arotor 14 is seecured to the axle 13 in any known manner and hasoppositely disposed annular braking surfaces 15 and 16.

In addition to the rotor 14 the brake assembly 11 includes a caliper,indicated generally by the reference numeral 17. The caliper 17 has legs18 and 19 that are juxtaposed to the rotor braking surfaces 15 and 16,respectively. The caliper legs 18 and 19 are integrally connected by abridging portion 21.

The caliper 17 is supported for sliding movement relative to the rotor14 in a direction parallel to the axis of rotation of the rotor 14. Thesliding support for the caliper 17 may be of any known type and includesa torque plate 22 that is affixed against rotation through action with amember 23 that is affixed to an axle housing 24.

A first brake pad, indicated generally by the reference numeral 25, isinterposed between the caliper leg 18 and the rotor braking surface 15.The first brake pad 25 includes a frictional lining 26 and a backingplate 27. The frictional lining 26 is secured to the backing plate 27 inany known manner, for example, by bonding. A second brake pad, indicatedgenerally by the reference numeral 28, is interposed between the caliperleg 19 and the rotor braking surface 16. The brake pad 28 includes africtional lining 29 and a backing plate 31 to which the lining 29 isaffixed in any known manner, for example, by bonding. The brake pad 28may be 'fixed against rotation relative to the caliper leg 19 or may beheld against rotation by the torque plate 22.

A hydraulic and mechanical actuator is provided for actuating the brakepad 25 and bringing its lining 26 into frictional engagement with therotor braking surface 15. The construction of this actuating mechanismwill become more apparent as this description proceeds. The actuatingmechanism also creates a reactive force upon the caliper 17 that causesit to slide in an axial direction whereupon its leg 19 presses the pad28 into frictional engagement with the rotor braking surface 16.

The hydraulic actuating means includes a cylinder bore 32 that is formedin the caliper leg 18 and which extends parallel to the axis of rotationof the rotor 14. A piston 33 is slidably supported in the bore 32 anddefines with the bore 32 a fluid chamber 34. The chamber 34 is adaptedto be selectively pressurized for effecting relative axial movementbetween the piston 33 and caliper 17.

The outer end of the piston 33 bears against a cam plate 35. The camplate 35 has outwardly extending flanges 36 and 37 (FIGS. 1 and 3) whichflanges are notched at 38 and 39. lnwardly extending flanges 41 and 42of the torque plate 22 extends into the notches 38 and 39 and hold thecam plate 35 against rotation while permitting axial movement of the camplate 35.

The outer extremities of the cam plate 35 are engaged with the brake padbacking 27 so that axial forces exerted by the piston 33 will betransmitted through the cam plate 35 to the backing plate 27. At thesame time an axial force is exerted upon the brake pad 25 by the piston33, a reactive force is exerted upon the caliper 17 for sliding it andactuating the brake pad 28. The brake pads 25 and 28 are, thereby,hydraulically actuated.

An annular cam element, indicated generally by the reference numeral 43is interposed between the cam plate 35 and the backing plate 27. The camelement 43 has a plurality (three) of circumferentially spaced pockets44 in which balls 45 are captured. The balls 45 also are captured inpockets 46 formed in the cam plate 35. On either side of the cam elementpockets 44, inclined ramps 47 (FIG. are formed.

The cam element 43 has an outturned tang 48 formed at its upperperiphery that is received in a slot 49 formed in the backing plate 27.The tang 48 is normally at one end of the slot 49 and thus limits theangular position of the cam element 43 in one of its extreme positions.

The cam element 43 has a downwardly extending projection 51 that has aboss 52 formed at its lower extremity. A flexible transmitter 53 isconnected to the boss 52 at one end. The opposite end of the flexibletransmitter 53 is connected to a suitable actuator (not shown)positioned within the drivers compartment of the vehicle. A returnspring 54 encircles the one end of the flexible transmitter 53 and bearsagainst the boss 52 and against a fixed abutment member 55 that is fixedrelative to the torque plate 22. The spring 54 normally urges the camelement 43 in a clockwise direction as viewed in FIG. 3.

In order to mechanically actuate the brake assembly 11, a pull isinserted upon the flexible transmitter 53. This pull causes the camelement 43 to rotate in a counterclockwise direction. The axis ofrotation of the cam element 43 is coincident with the axis of thecylinder bore 32. When the cam element 43 rotates, the balls 45 willengage the ramps 47 and an axial force will be exerted upon the camelement 43. This force is transmitted to the backing plate 27 andeffects axial movement of the brake pad 25 into engagement with therotor braking surface 15. At the same time, a reactive force is exertedthrough the balls 45 onto the cam plate 35. This force is transmittedthrough the piston 33 to the caliper 17 in a manner to be described andcauses the caliper 17 to slide in an axial direction. The slidingmovement brings the brake pad 28 into engagement with the rotor brakingsurface 16. When the pull on the cable 53 is released, the spring 54will return the cam element 43 to its retracted position.

In addition to providing for the mechanical and hydraulic actuation ofthe brake pads 25 and 28, brake assembly ll generates a self-energizingor servo force when mechanically actuated. To accomplish this, the camplate 35 is formed with a depressed central portion 56 formed by aconical surface 57. A ball 59 is normally positioned at the base of theconical surface 57. The ball 59 is larger in diameter than the balls 45.The backing plate 27 is formed with an embossment 61 that also receivesand captures the ball 59. It will be noted that the cam element 43 has acentral opening 52 that passes the embossment 61.

A pair of spaced apart rivets 63 and 64 are affixed to the backing plate27 within respective embossments 65 and 66. The rivets 63 and 64 haveenlarged diameter cylindrical portions 67 and 68 that are received instill larger diameter openings 69 and 71 formed in the cam plate 35.Snap rings 72 and 73 are affixed to the rivets 63 and 64 so as toprevent complete axial separation of the cam plate 35 from the backingplate 27. It should be noted that the cylindrical sections 67 and 68have sufficient length, however, so as to permit some relative axialmovement between the cam plate 35 and the backing plate 27. This axialmovement is permitted to allow for the mechanical actuation of thebrake. In addition, the larger diameter of the cam plate openings 69 and71 permits transverse movement of the brake pad 25 relative to the camplate 35 for a reason now'to be described.

When the brake pad 25 is actuated, it tends to rotate in the samedirection of rotation as the rotor 14. The size of the openings 69 and71 permits the backing plate 27 to shift transversely relative to thecam plate 35 during this relative movement. At this time, the ball 59will roll up the surface 57 in one direction or the other depending uponthe direction of rotation of the rotor 14. Due to the inclination of thesurface 57, an axial force component will be exerted upon the backingplate 27 when the brake is mechanically actuated. This force componentis only experienced during mechanical actuation since at this time thecam plate 35 does not exert any direct actuating force upon the brakepad 25.

Inward movement of the piston 33 is precluded during mechanicalactuation by means of a canted ring 75 (FIG. 6) that is interposedbetween the caliper 17 and piston 33 in a counterbore 76 of the former.The ring 75 is disposed at an angle relative to the axis of the cylinderbore 32 and permits free outward movement of the piston 33 and limitedinward movement. Any substantial inward movement of the piston 35 is,however, precluded by wedging of the ring 75 between the counterbore 76and the piston 33.

It should be readily apparent that the disclosed brake construction hasseveral advantages. A compact mechanical actuator which is interposedbetween the piston 33 and the brake pad 25 permits convenient mechanicalactuation. This mechanical actuation is accomplished with the forcebeing exerted along the same line as that exerted by the hydraulicactuator. This is possible without necessitating complicated seals suchas are required if the piston 33 were to be mechanically actuated. Inaddition, the mechanical actuated brake provides sufficient brakingaction since a selfenergizing force is exerted upon the brake pad 25when it is mechanically actuated.

It is to be understood that the foregoing description is that of apreferred embodiment of the invention.

Various changes and modifications may be made without departing from thespirit and scope of the invention as defined by the appended claims.

I claim:

1. A disk brake assembly for braking the rotation of an associated brakerotor comprising a caliper, at least one brake pad associated with saidcaliper and having a frictional lining adapted to engage the rotor, saidcaliper defining a fluid motor including a piston, and a mechanicalactuator interposed between said piston and said brake pad fortransmitting actuating forces from said piston to said brake pad and formechanically actuating said brake pad, said mechanical actuatorcomprising relatively movable elements, means for effecting relativemovement of said elements, means for exerting an axial force upon saidbrake pad upon relative movement of said elements, and means includingcooperating camming elements interposed between said piston and saidbrake pad for exerting a selfenergizing force upon said brake pad onlywhen said brake pad is actuated by said mechanical actuator.

2. A disk brake assembly as set forth in claim 1 further including meansfor preventing inward movement of the piston upon actuation of themechanical actuator.

3. A disk brake assembly as set forth in claim 1 wherein the mechanicalactuator comprises annular cam means including a pivotally supportedelement rotatable about a pivot axis aligned with the axis of thecylinder bore for effecting the relative movement.

4. A disk brake assembly as set forth in claim 3 wherein the annular cammeans includes a plurality of circumferentially spaced balls, the cammeans having pockets for receiving said balls and ramps for exerting theaxial force upon pivotal movement of the pivotally supported camelement.

5. A disk brake assembly as set forth in claim 4 wherein the cammingelements include a ball element interposed between elements of themechanical actuator and-the brake pad, said actuator elements havinginclined surfaces and being supported for relative movement in thedirection of rotor rotation for exerting the axial force upon suchrelative movement.

6. A disk brake assembly as set forth in claim 5 wherein the ballelement is concentrically disposed relative to the axis of rotation ofthe cam element.

1. A disk brake assembly for braking the rotation of an associated brakerotor comprising a caliper, at least one brake pad associated with saidcaliper and having a frictional lining adapted to engage the rotor, saidcaliper defining a fluid motor including a piston, and a mechanicalactuator interposed between said piston and said brake pad fortransmitting actuating forces from said piston to said brake pad and formechanically actuating said brake pad, said mechanical actuatorcomprising relatively movable elements, means for effecting relativemovement of said elements, means for exerting an axial force upon saidbrake pad upon relative movement of said elements, and means includingcooperating camming elements interposed between said piston and saidbrake pad for exerting a selfenergizing force upon said brake pad onlywhen said brake pad is actuated by said mechanical actuator.
 2. A diskbrake assembly as set forth in claim 1 further including means forpreventing inward movement of the piston upon actuation of themechanical actuator.
 3. A disk brake assembly as set forth in claim 1wherein the mechanical actuator comprises annular cam means including apivotally supported element rotatable about a pivot axis aligned withthe axis of the cylinder bore for effecting the relative movement.
 4. Adisk brake assembly as set forth in claim 3 wherein the annular cammeans includes a plurality of circumferentially spaced balls, the cammeans having pockets for receiving said balls and ramps for exerting theaxial force upon pivotal movement of the pivotally supported camelement.
 5. A disk brake assembly as set forth in claim 4 wherein thecamming elements include a ball element interposed between elements ofthe mechanical actuator and the brake pad, said actuator elements havinginclined surfaces and being supported for relative movement in thedirection of rotor rotation for exerting the axial force upon suchrelative movement.
 6. A disk brake assembly as set forth in claim 5wherein the ball element is concentrically disposed relative to the axisof rotation of the cam element.